The ability to find and rescue a person in trouble often times is a matter of a critical time period. For example, the time to find and rescue a downed fireman is very critical and limited depending on the oxygen he/she may have left along with the fire ground situation itself. If a firefighter is hurt, and is within a fire ground situation, the situation and personal safety of the person can degrade very quickly. Time is ‘the’ critical factor in bringing a firefighter out of a situation alive.
Finding a lost fire fighter in a commercial or residential fire is often very difficult. The rescue methods used in today's firefighting are very basic. One method is to follow the person's hose line, assuming they are on one. Many fire situations have a plurality of hoses at the scene and finding one person on one hose in a timely manner is not an easy task. If the downed or lost person has a personal alert safety system (PASS), then following the audible signal emitted by the PASS will hopefully find the person in trouble. Some PASS systems also have an optional visual light to help find a person, assuming you can see well enough as you near the person in trouble. A PASS system is usually worn as part of a firefighters self-contained breathing apparatus (SCBA).
A PASS system has a purpose to sound a loud, highly discernible audio alarm if a distress condition occurs. The device will sense an absence of motion if the wearer becomes immobilized for about 25 seconds. It will also activate at a preset “low air” condition, usually about 10% or 10 minutes. Its alarm must function in the manual or automatic mode to assist rescue crews in locating the firefighter in distress. PASS devices must be highly reliable and easy to operate. They usually require an alarm sound output of at least 95 dBA, measured at ten feet. Two important parameters of sound that must be considered are sound intensity (loudness) and sound discernability (the ability to recognize a particular sound in a high background noise environment). Some of the earlier PASS devices had a loud sound, but were difficult to distinguish above the noise associated with the typical fire ground. Present day PASS devices have helped overcome the problem of locating the source of the sound signal by modulating a pure tone, or generating a sound that consists of several intermittent tones or use of a sweep frequency. A sweep frequency type of sound will generate multiple tones that sweep from 2,000 cycles thru 6,000 cycles so as to be not easily masked by background noise.
The main sensor that permits a PASS device to operate in the automatic mode is called the motion sensor transducer. This is the heart of the PASS device. If the sensor is not sensitive enough to sense random motion, the device will constantly go into pre-alert, becoming a nuisance to firefighters and may discourage activation. The ideal sensor is one that only requires normal motion to keep the PASS inhibited, yet is sensitive enough to immediately sense a lack of motion when a firefighter is immobilized. If a firefighter disables the PASS system, it leaves he/she at risk.
There are a number of methods of sensing motion. Some PASS manufacturers use mechanical devices, such as a small metal ball to sense motion. The random motion of the ball is converted into an electrical signal as long as motion exists. Another popular method to sense motion is accomplished by the closing of a mercury filled switch. Still another method uses a ball inside an infrared light chamber. The motion of the ball interrupts the light signal and is sensed as motion. Perhaps the most progressive method involves a solid-state accelerometer device that can sense a broad range of motion, and is not position sensitive.
Most PASS manufacturers use a custom microchip or a microprocessor to process the signal. Some chip functions are sensing low battery, motion, sound, and light generation. A quartz crystal may be used to ensure accurate timing. Switching is another aspect of PASS alarms. PASS alarms are required to be automatically switched from the ‘storage mode’ to the ‘sensing mode’, without independent action by the wearer. Many manufacturers use a mechanical switch to activate their PASS devices. A recent improvement is all-electronic switching. These switches must be reliable and easy to operate, even with a gloved hand. A properly used PASS will save lives.
The major problem with a PASS system in itself is that it does not always allow for a rescuer to have the ability to quickly pinpoint a downed person. Another problem is in the case of a plurality of downed firefighters. A plurality of audible alarms would tend to disorient a rescuer and also not give a rescuer the ability to know how many firefighters may be down or in trouble. Nor would a rescuer(s) know how close they would be to the downed person. In fire situations, smoke can become so heavy as to not allow a rescuer to be able to see very far in front.
The present invention solves these aforementioned problems by allowing for a radio signal to be initiated when a firefighter is in trouble, also allowing for each firefighter to have a special decoded signal. Decoded signals would allow a base unit to know exactly how many people are in trouble, and also their temperatures, other vital measurements, and room temperature of the firefighter. The present invention provides a radio frequency signal that allows the rescuer(s) to know the direction, range and number of firefighters that are in trouble. The present invention can be a stand-alone device or can be integrated and triggered by a PASS system thus making use of the motion detection and/or air low alerts within the PASS itself. The present invention allows for direction and range of firefighter(s) in trouble and can help save lives by reducing the time it takes to perform a rescue.